Spider bite on finger at first was itchy& painful at touch now 3 weeks later bullseye effect allergys up shorness of breath viens around bite noticabl?

Something else... ...Is going on here. Spider bites shouldn't last for 3 weeks unless they get infected (which may have happened) -- but shortness of breath does not fit the picture at all. Do you know for a fact that it was a spider bite? It could have been something else entirely. See your doctor; the shortness of breath alone deserves an examination.
Spider bite? Without a picture this is difficult to answer, but if you're still having significant symptoms 3 weeks after the bite, you need to have it checked by a doctor.